Performance Assessment of Two Different Aviation CARC Coating Systems on Steel When Cadmium Plating Is Eliminated

Corrosion-test specimens of AISI 4130 and 4340 steel with and without cadmium plating were prepared for evaluation using two different aviation versions of the chemical agent resistant coating system. Both coating systems used MIL-PRF-23377 high solids primer and MIL-DTL-64159 type II waterborne topcoat. One system incorporated the established MIL-PRF-23377 primer formula with hexavalent chromium (class C), while the other utilized an improved nonchromate (class N) MIL-PRF-23377 formulation that recently passed the specification performance criteria. The 4130 steel specimens were used to assess performance for general corrosion, throwing power, and crevice corrosion all under GM 9540P accelerated cyclic-corrosion conditions. In addition, thick 4130 steel panels were prepared using a variety of surface preparation conditions to assess pull-off coating adhesion, in accordance with ASTM-D-4541. AISI 4340 material was fabricated in accordance with ASTM-F-519. Type 1d C-rings were utilized to assess hydrogen embrittlement tolerance differences between the various coating systems under GM 9540P conditions.
(Note: the complete reference information for all standards and specifications mentioned here can be found in the report.)